Ultrasonic flow meter having flow conditioning arrangements for flow controlling in a linear fluid conduit

ABSTRACT

The subject matter of this specification can be embodied in, among other things, a fluid flow conditioning apparatus that includes a linear fluid conduit having a first tubular body defining a major axis and extending from a conduit inlet to a conduit outlet arranged opposite the conduit inlet, and configured with a predetermined flow geometry to define a linear fluid flow path along the major axis, a fluid inlet non-parallel to the linear fluid flow path, a first fluid flow conditioner configured to receive fluid flow, condition fluid flow, and redirect conditioned fluid flow along the linear fluid flow path along the major axis, a second fluid flow conditioner configured to receive fluid flow from the linear fluid flow path along the major axis, redirect fluid flow away from the linear fluid flow path, and condition fluid flow.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This application claims the benefit of priority to U.S. ProvisionalApplication No. 63/062,681, filed Aug. 7, 2020, and U.S. ProvisionalApplication No. 63/162,163, filed Mar. 17, 2021, the contents of whichare incorporated by reference herein.

TECHNICAL FIELD

This instant specification relates to ultrasonic fluid mass flowsensors.

BACKGROUND

Fluid measurement devices are used for the characterization andoperation of fluid control systems. As the dynamic bandwidths, flowranges, accuracies, and reliabilities of flow measurement devicesimprove, the potential application landscape of such devices broadens.High dynamic bandwidth flow meters can be used as control systemfeedback sensors for improving steady state and/or transient accuracy infuel systems. Ultrasonic flow meters (USFM) are a proven industrialtechnology that can be leveraged for implementation to aircraft turbinesystems.

Existing time of flight ultrasonic flow meters are used in the racingand automotive industries, pipeline custody transfer, industrial flowmeasurement, and many other applications. However, many of theseapplications encompass steady-state flow conditions, and theirrespective applications allow for volumetric flow measurement. In otherapplications, such as aircraft gas turbine engine applications, thefluid environmental conditions of the fuel delivery system imposessignificant design challenges.

In the art of fuel flow meters (primary element) flow conditioning offuel is necessary for controllability of the fuel flow entering andleaving the meter to achieve desired flow meter performance, accuracy,and adequate turn down ratios. As a general rule of thumb of fluiddynamics, for a given diameter of pipe it can take 10 or more lengths ofstraight pipe following a disturbance for a fluid flow to stabilize(e.g., a length-to-diameter, L/D, ratio of about 10 or greater).

SUMMARY

In general, this document describes ultrasonic fluid mass flow sensors.

In an example embodiment, a fluid flow conditioning apparatus includes alinear fluid conduit having a first tubular body defining a major axisand extending from a conduit inlet to a conduit outlet arranged oppositethe conduit inlet, and configured with a predetermined flow geometry todefine a linear fluid flow path along the major axis, a fluid inletdefining an inlet fluid flow path that is non-parallel to the linearfluid flow path, a first fluid flow conditioner having a firstconditioner inlet in fluidic communication with the fluid inlet, and afirst conditioner outlet in fluidic communication with the conduitinlet, and configured to receive fluid flow through the firstconditioner inlet along the inlet fluid flow path, condition, by thefirst conditioner inlet, fluid flow, and redirect conditioned fluid flowaway from the inlet fluid flow path and through the first conditioneroutlet along the linear fluid flow path along the major axis, a secondfluid flow conditioner having a second conditioner inlet in fluidiccommunication with the conduit outlet, and a second conditioner outlet,and configured to receive fluid flow from the linear fluid flow pathalong the major axis, redirect fluid flow away from the linear fluidflow path and through the second conditioner outlet along an outletfluid flow path that is non-parallel to the linear fluid flow path, andcondition, by the second conditioner outlet, fluid flow, and a fluidoutlet configured to receive fluid flow from the second conditioneroutlet.

Various embodiments can include some, all, or none of the followingfeatures. The first fluid flow conditioner can include a second tubularbody extending between a first longitudinal end and a secondlongitudinal end opposite the first longitudinal end, wherein the firstconditioner inlet is arranged along the second tubular body, and thesecond longitudinal end defines the first conditioner outlet. The firstconditioner inlet can include a collection of ports defined radiallythrough the second tubular body. The fluid flow conditioning apparatuscan include a sensor apparatus arranged proximal to the firstlongitudinal end. The sensor apparatus can include an ultrasonictransducer apparatus configured to emit and receive ultrasonic signalsalong the linear fluid flow path. The sensor apparatus can include asensor housing having an interior surface defining a sensor axis and anaxial interior sensor housing cavity including a first axial sensorhousing portion having a first cross-sectional area perpendicular to thesensor axis, a second axial sensor housing portion arranged adjacent tothe first axial sensor housing portion along the sensor axis and havinga second cross-sectional area larger than the first cross-sectional areaperpendicular to the sensor axis, and a face extending from the interiorsurface of the first axial sensor housing portion to the interiorsurface of the second axial sensor housing portion, a buffer rod havinga first axial end and a second axial end opposite the first axial endand including a first axial buffer portion arranged within the firstaxial sensor housing portion and including the first axial end, a secondaxial buffer portion arranged within the second axial sensor housingportion and abutting the face, and including the second axial end, and athird axial buffer portion, extending axially between the first axialbuffer portion and the second axial buffer portion, and having a thirdcross-sectional area, smaller than the first cross-sectional area,perpendicular to the sensor axis, a cavity defined between the interiorsurface and the third axial buffer portion, and an acoustic transceiverelement acoustically mated to the first axial end. The second fluid flowconditioner can include a second tubular body extending between a firstlongitudinal end and a second longitudinal end opposite the firstlongitudinal end, wherein the second conditioner outlet is arrangedalong the second tubular body, and the first longitudinal end definesthe second conditioner inlet. The second conditioner outlet can includea collection of ports defined radially through the second tubular body.The fluid flow conditioning apparatus can include a sensor apparatusarranged proximal to the second longitudinal end. The sensor apparatuscan include an ultrasonic transducer apparatus configured to emit andreceive ultrasonic signals along the linear fluid flow path. The linearfluid conduit can be configured to dampen ultrasonic acoustic signals.The linear fluid conduit can include a tubular outer housing having afirst predefined geometry, and a removable inner housing arrangedconcentrically within the tubular outer housing and defining thepredetermined flow geometry.

In an example implementations, a method of fluid flow conditioningincludes receiving a fluid flow, flowing along a first fluid flow path,conditioning the fluid flow by flowing the fluid flow through a firstconditioner inlet of a first fluid flow conditioner, redirecting, by thefirst fluid flow conditioner, the fluid flow away from the first fluidflow path and toward a linear fluid flow path, flowing the fluid flowalong the linear fluid flow path through a first conditioner outlet,flowing the fluid flow along the linear fluid flow path through a fluidconduit having a first tubular body extending from a conduit inlet to aconduit outlet arranged opposite the conduit inlet, and configured witha predetermined flow geometry, flowing the fluid flow through a secondconditioner inlet of a second fluid flow conditioner along the linearfluid flow path, redirecting, by the second fluid flow conditioner, thefluid flow away from the linear fluid flow path and toward a secondfluid flow path, and conditioning the fluid flow by flowing the fluidflow through a second conditioner outlet of the second fluid flowconditioner.

Various implementations can include some, all, or none of the followingfeatures. The method can include transmitting an ultrasonic signalthrough the first conditioner outlet, the fluid conduit, and the secondconditioner inlet along the linear fluid flow path, receiving theultrasonic signal through the second conditioner inlet, and determiningat least one of a mass flow rate and a volume flow rate of the fluidflow based on the received ultrasonic signal. The first fluid flowconditioner can include a second tubular body extending between a firstlongitudinal end and a second longitudinal end opposite the firstlongitudinal end, wherein the first conditioner inlet is arranged alongthe second tubular body, and the second longitudinal end defines thefirst conditioner outlet. The first conditioner inlet can include acollection of ports defined radially through the second tubular body,and conditioning fluid flow by flowing through a first conditioner inletof a first fluid flow conditioner can include flowing the fluid flowthrough the collection of ports. The method can include at least one oftransmitting and receiving, by an ultrasonic transducer, an ultrasonicsignal through the first conditioner outlet and the fluid conduit alongthe linear fluid flow path, wherein the first fluid flow conditioneralso includes the ultrasonic transducer arranged proximal to the firstlongitudinal end. The second fluid flow conditioner can include a secondtubular body extending between a first longitudinal end and a secondlongitudinal end opposite the first longitudinal end, wherein the secondconditioner outlet is arranged along the second tubular body, and thesecond conditioner inlet is arranged proximal to the conduit outlet. Thesecond conditioner outlet can include a collection of ports definedradially through the second tubular body, and conditioning fluid flow byflowing fluid through a second conditioner outlet of a second fluid flowconditioner also includes flowing the fluid flow through the collectionof ports. The method can include at least one of transmitting andreceiving, by an ultrasonic transducer, an ultrasonic signal through thesecond conditioner outlet and the fluid conduit along the linear fluidflow path, wherein the second fluid flow conditioner also includes theultrasonic transducer arranged proximal to the second longitudinal end.

The systems and techniques described here may provide one or more of thefollowing advantages. First, a system can provide improved environmentalsurvivability against wide fluid temperature ranges. Second, the systemcan provide improved environmental survivability against wide fluidpressure ranges. Third, the system can provide improved environmentalsurvivability against harsh fluids. Fourth, the system can provideintegral fluid density sensing. Fifth, the system can be relativelyunaffected by fluid flow dynamics (e.g., swirl, vortices, instability).Sixth, the system can be used with update rates of 100 Hz or greater,while maintaining accuracy. Seventh, the system can provide increasedflow meter accuracy. Eighth, the system can provide improved sensorreliability.

The details of one or more implementations are set forth in theaccompanying drawings and the description below. Other features andadvantages will be apparent from the description and drawings, and fromthe claims.

DESCRIPTION OF DRAWINGS

FIG. 1 is a cross-sectional diagram of an example ultrasonic flowmeasurement system.

FIG. 2A is a cross-sectional diagram of an example ultrasonic sensormodule of the system of FIG. 1 .

FIG. 2B shows a conceptual example of reflective surface areas in theexample ultrasonic sensor module of FIG. 2A.

FIG. 3 shows a conceptual example of incident wave propagation in themodule of FIG. 2A.

FIG. 4 shows a conceptual example of fluid pressure mitigation in themodule of FIG. 2A.

FIGS. 5A-5C show conceptual examples of incident wave traversal in anultrasonic flow measurement system.

FIGS. 6A and 6B are graphs that show example incident waves and echoesin the ultrasonic flow measurement system of FIG. 1 .

FIG. 7 is a flow chart that shows an example of a process fordetermining a fluid reflection coefficient.

FIG. 8 is a flow chart that shows an example of a process fordetermining a mass fluid flow.

FIG. 9 is a flow chart that shows an example of a process for resistingeffects of fluid exposure on the acoustic transducer of the module ofFIG. 2A.

FIG. 10 is a schematic diagram of an example of a generic computersystem.

FIG. 11 is a cross-sectional diagram of an example baseline ultrasonicflow measurement system.

FIG. 12 is a cross-sectional diagram of an example ultrasonic flowmeasurement system having a flow insert.

FIG. 13A is a cross-sectional diagram of an example ultrasonic flowmeasurement system having flow conditioners.

FIG. 13B is cylindrical projection view of an example flow conditionerconfiguration.

FIG. 14A is a cross-sectional diagram of another example ultrasonic flowmeasurement system having flow conditioners.

FIG. 14B is cylindrical projection view of another example flowconditioner configuration.

FIG. 15A is a cross-sectional diagram of another example ultrasonic flowmeasurement system having flow conditioners.

FIG. 15B is cylindrical projection view of an example inlet flowconditioner configuration.

FIG. 15C is a cylindrical projection view of an example outlet flowconditioner configuration.

FIG. 16A is a cross-sectional diagram of another example ultrasonic flowmeasurement system having flow conditioners.

FIG. 16B is cylindrical projection view of an example inlet flowconditioner configuration.

FIG. 16C is a cylindrical projection view of an example outlet flowconditioner configuration.

FIG. 17 is a collection of example computational fluid dynamics modelsof fluid flows through the example ultrasonic flow measurement systemsof FIGS. 11-16C.

FIG. 18 is a collection of cylindrical projection views of additionalexample outlet flow conditioner configurations.

FIG. 19 is a flow chart that shows an example of a process forconditioning fluid flow in an example ultrasonic flow measurementsystem.

DETAILED DESCRIPTION

This document describes ultrasonic fluid mass flow sensor (USFM)systems, and techniques for measuring fluid flow characteristics offluids. In general, the USFM systems described in this system can beused in fluid environments that would degrade or destroy existing USFMsystems. The fluid environmental conditions of fuel delivery systems canimpose significant design challenges. For current, state of the art,aircraft and other gas turbine engine applications, an ultrasoundtransducer deployed for such applications will be expected to survivehigh fluid pressures (e.g., 0 psi to 4000 psi or higher) and a widerange of fluid temperatures, including high fluid temperatures (e.g.,−65 degrees F. or lower to 325 degrees F. or higher).

These temperatures and pressures are far more challenging than thepressures and temperatures that are typically encountered in industrialfluid, steam, or pipeline custody transfer applications. To remaineffective in such applications, a wetted transducer must also not bedegraded by long-term immersion in caustic fluids such as aircraft fuelsand/or additives at high temperatures and/or pressures. The USFM systemsdescribed in this document include features that improve thesurvivability of the USFM under such conditions.

In existing industrial and custody transfer USFM systems based on timeof flight, cross-correlation, and phase shift measurements have accuracylimitations determined by the flow velocity range, or turn-down ratio,within the flow measurement volume. For example, during low flowconditions the difference between upstream and downstream measurementscan be too insensitive to maintain a target accuracy. During high flowconditions, measurement accuracy can suffer from flow instabilities,often caused by the acoustic path being off-axis with respect to theflow, flow separation, and/or non-axisymmetric flow conditions. Off-axistransducer configurations can also cause sensitivity and accuracyproblems. Round transducers can impose non-uniform ultrasound fields asthe waves pass diagonally through the flow, reducing accuracy. Inexisting USFM systems having ultrasound beams smaller than the flowcross-section, the full flow profile is not insonified and thereforemust be estimated, typically with a single K-factor correction value, ora complex coefficient matrix for USFM systems using multiple sonicpaths, such as in natural gas custody transfer applications. In existingUSFM designs, flow measurement accuracy can be difficult to maintainover a large turndown ratio when the flow regime is unstable, or changessubstantially from laminar to turbulent flow. For example, some existingindustrial USFM systems have a practical turndown ratio of no more than50:1 while maintaining accuracy, even when application piping and flowconditioning are executed ideally. By comparison, a gas turbine fuelsystem can require a substantially higher turndown of generally 100:1,with some applications upward of 350:1 or more. In addition, a gasturbine flow measurement system must be capable of maintaining dynamicaccuracy, with update rates of 100 Hz or more.

Mass flow is critical to the combustion process to maintain a safe andoperable fuel to air ratio. Excess fuel to air ratio can lead tocompressor surge or over temperature events. Conversely, excess air tofuel can lead to compressor blow out. Either of these events can bedetrimental to gas turbine performance and are therefore key designdrivers for gas turbine engine design. Additionally, some applicationssuch as gas turbine engines are designed to operate on various fueltypes under varying pressures and temperatures.

An important variable, especially in aircraft gas turbine applications,is the variation in fuel specific gravity amidst the fuel types andtemperatures. In some applications, the expected fuel specific gravitycan vary by approximately 25% across expected temperature ranges anduseable fuel types. The wide range in fuel density, if unknown, willdrive a broad range in mass fuel flow for a given volumetric flow rate.This variability can lead to large variances in mass air to fuel flowratios, making engine design across the environmental range inefficient,yielding oversized engines, conservative acceleration and/ordeceleration schedules, excessive surge margins, and/or excessiveblowout margins.

FIG. 1 is a cross-sectional diagram of an example of an ultrasonic flowmeasurement (USFM) system 100. The USFM system 100 includes a fluidhousing 110 and two ultrasonic sensor modules 200. The fluid housing 110includes an axial fluid housing cavity 120 a defined by an interiorsurface 121 a, and an axial fluid housing cavity 120 b defined by aninterior surface 121 b. A fluid port 122 a defines a fluid path 124 aconnected to the fluid cavity 120 a. A fluid port 122 b defines a fluidpath 124 b connected to the fluid cavity 120 b. The fluid housing 110also defines a cavity 126 that extends between the fluid cavity 120 aand the 120 b.

The fluid housing 110 also includes a fluid control conduit 130 thatdefines a fluid path 132 along a conduit axis 134. The fluid controlconduit 130 fluidically connects the fluid cavity 120 a and the fluidcavity 120 b, putting the fluid cavity 120 a in fluidic communicationwith the fluid cavity 120 b. The fluid control conduit 130 has apredetermined flowable area 136 and shape (e.g., square, tapered, and/orcurved edges, parallel or tapered walls, to affect fluid flow behavior).In some implementations, the fluid housing 110 can be used across manyapplications, and the fluid control conduit 130 can be aninterchangeable, specialized subcomponent (e.g., an adapter) that canadapt the USFM system 100 for particular fluid types, applications,and/or operational conditions.

Referring now to FIG. 2A, an enlarged cross-sectional diagram of theexample ultrasonic sensor module 200 of the system of FIG. 1 is shown.The ultrasonic sensor module 200 includes a sensor housing 202 having anaxial interior sensor housing cavity 204 and a sensor axis 206 definedby an interior surface 207. When the ultrasonic sensor module 200 isassembled to the fluid housing 110 of FIG. 1 , the sensor axis 206 issubstantially aligned with the conduit axis 134. The sensor housing 202has an axial sensor housing portion 208 a having a cross-sectional area209 a perpendicular to the sensor axis 206. The sensor housing 202 alsohas an axial sensor housing portion 208 b having a cross-sectional area209 b perpendicular to the sensor axis 206. The cross-sectional area 209b is dimensionally larger than the cross-sectional area 209 a. A face210 extends from the interior surface 207 of the axial sensor housingportion 208 a to an interior surface 208 of the axial sensor housingportion 208 b. In the illustrated example, the face 210 is formed as asubstantially squared shoulder or ledge at the transition between thecross-sectional area 209 a and the cross-sectional area 209 b. In someembodiments, the face 210 can be a tapered or otherwise non-squaredtransition between the cross-sectional area 209 a and thecross-sectional area 209 b.

The ultrasonic sensor module 200 also includes an acoustic transceiverelement 230. The acoustic transceiver element 230 is configured to emitacoustic vibrations (e.g., ultrasonic sounds waves) at a predeterminedwavelength (λ) when energized. In some embodiments, a separate acousticdriver and acoustic receiver may be implemented as the acoustictransceiver element 230. In some embodiments, the acoustic transceiverelement 230 can be configured to detect received acoustic vibrationsalso. In some embodiments, the acoustic transceiver element 230 can be apiezo element.

The acoustic transceiver element 230 is acoustically mated with orotherwise abutted to an axial end 252 of a buffer rod 250 by a bondinglayer 232. In some embodiments, the bonding layer 232 can be an adhesivelayer. In some embodiments, the buffer rod can be made of anyappropriate material or combination of materials that can provide properacoustic impedance ratios when combined with matching layer material toimprove or maximize sensitivity of measurements, are cost effective, canbe fabricated within reasonable manufacturing tolerances, and/or providegood mechanical and chemical compatibility in the intended applicationenvironment. Examples of buffer rod materials include titanium alloys,austenitic stainless steel, aluminum, borosilicate glasses, fused (e.g.,non-crystalline) quartz, and technical ceramics (e.g., AlN, Al₃O₃, SiN,and blends).

In some embodiments, the bonding layer 232 can be omitted, with theacoustic transceiver element 230 in direct contact with the axial end252. For example, the acoustic transceiver element 230 can be held inplace by a mechanical clamp or other appropriate fixation assembly, orthe acoustic transceiver element 230 can be held in place by fixationfeatures formed in the interior surface 207. In some embodiments, thebonding layer 232 can be formed from a highly ductile material, such asgold or lead, which can be conformed to the mating faces of the acoustictransceiver element 230 and the axial end 252.

The acoustic transceiver element 230 is backed by a backing 234. Thebacking 234 has a predetermined form and is made of a material thatimproves the sensitivity and/or efficiency of the acoustic transceiverelement 230.

The buffer rod 250 extends along the sensor axis 206 from the axial end252 to an axial end 254 opposite the axial end 252. The buffer rod 250has a predetermined axial length of about a round multiple of one-halfof the transmission wavelength of the acoustic transceiver element 230(n/2 λ). The buffer rod 250 includes an axial buffer portion 256 aarranged within the axial sensor housing portion 208 a and includes theaxial end 252. The buffer rod 250 includes an axial buffer portion 256 barranged within the axial sensor housing portion 208 b and includes theaxial end 254. In some embodiments, the axial buffer portion 256 b cancontact the interior surface directly or indirectly (e.g., through aseal, sleeve, or bonding material) to substantially seal the sensorcavity 204 from fluid incursion at the axial end 254.

The buffer rod 250 also includes an axial buffer portion 256 c thatextends axially between the axial buffer portion 256 a and the axialbuffer portion 256 b. The axial buffer portion 256 c has across-sectional area 209 c that is smaller than the cross-sectional area209 a perpendicular to the sensor axis 206. A cavity 260 is definedbetween the interior surface 207 and the axial buffer portion 256 c. Thecavity 260 is partly defined by a face 262 defined between the axialbuffer portion 256 a and the axial buffer portion 256 c. The face 262 isa predetermined distance from the axial end 252. Referring to FIG. 2B,the cross-sectional area 209 a is about twice as large as thecross-sectional area 209 c. In other words, the area within axial bufferportion 256 c is about the same as the area of the face 262.

The buffer rod 250 has a predetermined acoustic impedance (Z_(buffer)).In the illustrated example, the cavity 260 is filled with air (e.g., anair gap), a fluid (e.g., oil), or a solid having an acoustic impedancethat is sufficiently different from the acoustic impedance of the bufferrod 250 to reflect an acoustic echo when struck by an acoustic wave(e.g., an ultrasonic ping). In some embodiments, the cavity 260 isevacuated to form at least a partial vacuum.

In the illustrated example, the axial buffer portion 256 a is partlytapered, and is covered by a cladding 270. The taper has a predeterminedshape that is configured to improve the efficiency and/or sensitivity ofthe ultrasonic sensor module 200 by directing the propagation ofincident waves. The cladding 270 is configured to improve the efficiencyand/or sensitivity of the ultrasonic sensor module 200 by directing thepropagation of incident waves, acoustically isolating the buffer rod 250from the sensor housing 202, and/or thermally insulating the buffer rod250 from the sensor housing 202. In some embodiments, the taper, thecladding, or both may be omitted. In some embodiments, other portions ofthe buffer rod 250 may include a cladding.

Referring again to FIG. 2A, the ultrasonic sensor module 200 includes amatching layer 280 acoustically mated with, affixed to, or otherwiseabutted to the axial end 252 of the buffer rod 250. In some embodiments,the matching layer 280 may be adhered to the axial end 252. In someembodiments, portions of the matching layer 280 may extend to the sensorhousing 202 and be affixed (e.g., welded) to the sensor housing 202. Insome embodiments in which the matching layer 280 is affixed to thesensor housing 202, the joint between the matching layer 280 and thesensor housing 202 can substantially seal the sensor cavity 204 fromfluid incursion at the axial end 254. The matching layer 280 has anaxial thickness that is about a round odd multiple of the transmissionwavelength of the acoustic transceiver element 230 (n/4 λ), for example¼ λ.

Referring again to FIG. 1 , the two ultrasonic sensor modules 200 faceeach other across the fluid control conduit 130. The acoustic transducerelements of the ultrasonic sensor modules 200 are separated by apredetermined distance 150.

The USFM system 100 includes a controller 190. The controller 190includes circuitry configured to activate the ultrasonic sensor modules200 to cause acoustic incident waves to be emitted, to detect thereception of acoustic waves at the ultrasonic sensor modules 200,measure the timings between transmission and reception of variouscombinations of direct and reflected acoustic waves, and/or determinevarious properties of the USFM system 100 and/or the fluid based in parton those measured timings as will be discussed further in thedescriptions of FIGS. 3-9 .

In use, a fluid is flowed through the USFM system 100. For example, afluid such as fuel can be provided at the fluid port 122 a where it willflow along the fluid path 124 a into the fluid cavity 120 a. The fluidflows around the ultrasonic sensor module 200 to the fluid controlconduit 130. The fluid flows through the fluid control conduit 130 alongthe fluid path 132 and then flows around the ultrasonic sensor module200 to the fluid cavity 120 b. The fluid then flows along the fluid path124 b out the fluid port 122 b. As will be discussed further in thedescriptions of FIGS. 3-9 , the ultrasonic sensor modules 200 areprotected from direct exposure to the fluid, and are used to transmitacoustic waves through the fluid to determine properties of the fluid,such as acoustic impedance, volume flow, and mass flow.

FIG. 3 shows a conceptual example of incident wave propagation in theultrasonic sensor module 200 of FIG. 2A. In use, the acoustictransceiver element 230 is activated to emit an incident wave (e.g., aping). The incident wave is transmitted into and along the buffer rod250. A portion of the incident wave, represented by arrow 310, travelsuntil it encounters the face 262. The junction of the face 262 and thecavity 260 causes a portion of the incident wave 310 to be reflected asan echo represented by arrow 320. The echo 320 travels back to bedetected by the acoustic transceiver element 230. In some embodiments,the ultrasonic sensor module 200 may include a separate acoustic emitterand receiver for transmission and detection of the incident waves.

Another portion of the incident wave, represented by arrow 330, travelsuntil it encounters the axial end 254. The junction of the axial end anda fluid 301 at the axial end 254 causes a portion of the incident wave330 to be reflected as an echo represented by arrow 340. The echo 340travels back to be detected by the acoustic transceiver element 230.Another portion of the incident wave, represented by arrow 350,propagates into the fluid 301 at the axial end 254.

The time between the transmission of the incident wave and detection ofthe echo 320 is measured (e.g., by the example controller 190 of FIG. 1) to determine a first time of flight. The time between the transmissionof the incident wave and detection of the echo 340 is measured todetermine a second time of flight. The amplitudes of the echo 320 andthe echo 340 are also measured. As will be discussed further in thedescriptions of FIGS. 6A-7 , the measured times-of-flight, the measuredecho amplitudes, and predetermined information about the acousticimpedance of the buffer rod 250 and predetermined distances between theacoustic transceiver element 230, the face 262, and the axial end 254,can be used to determine properties of the fluid 301 at the axial end254, such as acoustic impedance (Z_(fluid)) and/or speed of sound in thefluid (C_(fluid)).

In some implementations, the ultrasonic sensor module 200 can be used inapplications other than the USFM system 100. For example, the ultrasonicsensor module 200 can be put into contact with a fluid (e.g., attachedto or submerged in a tank, pipe, or other fluid vessel or volume) andcan be sonified as part of a process to determine an acoustic impedanceof the fluid, a speed of sound in the fluid, and/or a fluid density ofthe fluid.

In some implementations, characteristics of the buffer rod 250 itselfcan be determined based on the measured times-of-flight and/or themeasured echo amplitudes (e.g., to calibrate for unknown buffer rodacoustic impedance and/or compensate for the effects of temperaturechanges on the ultrasonic sensor module 200). Similarly, in someimplementations, the distances between the acoustic transceiver element230 and one or both of the face 262 and/or the axial end 254 can bedetermined based on the measured times of flight, the measured echoamplitudes, known distances, known buffer rod acoustic impedance, and/orknown buffer rod temperature.

FIG. 4 shows a conceptual example of fluid pressure mitigation in theultrasonic sensor module 200 of FIG. 2A. In use, the ultrasonic sensormodule 200 is at least partly exposed to the fluid 301 at the axial end254. In some embodiments, the temperature or chemical properties of thefluid 301 can be damaging to the acoustic transceiver element 230,therefore the ultrasonic sensor module 200 is configured to prevent thefluid 301 from coming into direct contact with the acoustic transceiverelement 230. For example, direct or indirect (e.g., though a shim,sleeve, cladding, seal, or sealant) contact between the axial bufferportion 256 b and the axial sensor housing portion 208 b and/or betweenthe buffer rod 250 and the face 210 can substantially block fluid flowfrom the axial end 254 to the acoustic transceiver element 230. In someimplementations, fluid seepage that gets by the buffer rod 250 can bedirected to the sensor cavity 204 without contacting a major face of theacoustic transceiver element 230.

In use, the ultrasonic sensor module 200 is at least partly exposed tofluid pressure, represented by arrows 410, at the axial end 254. Thefluid pressure 410 is a static fluid pressure relative to the dynamicpressures caused by the acoustic signals used by the acoustictransceiver element 230. In some embodiments, direct or indirect (e.g.,through the buffer rod 250 ) application of the fluid pressure 410 couldcreate a compressive force against the acoustic transceiver element 230that could offset or otherwise negatively affect signals provided by theacoustic transceiver element 230 in response to sensed acoustic signals.In some implementations, such effects can be compensated for bymathematically or by electrically offsetting the sensor signals in orderto recover an approximation of the true signal.

The ultrasonic sensor module 200 is configured to prevent the fluidpressure 410 from affecting the acoustic transceiver element 230. Forexample, the acoustic transceiver element 230 is acoustically mated tothe axial end 252. As such, the acoustic transceiver element 230 is ableto “float” on the buffer rod 250 relative to the sensor housing 202 andnot become compressed by the fluid pressure 410.

The acoustic transceiver element 230 is also protected from the fluidpressure 410 by the mechanical configuration of the buffer rod 250 andthe sensor housing 202. Fluid pressure 410 is applied to the axial end254, which urges movement of the buffer rod 250 into the sensor cavity204. This pressure that urges such movement is represented by arrows420. Movement of the buffer rod 250 is prevented by contact between theaxial buffer portion 256 b and the face 210 of the sensor housing 202,as represented by arrows 430. As such, the force 420 is prevented fromreaching the acoustic transceiver element 230.

The smaller size of the cross-sectional area 209 a is sized toaccommodate acoustic transceiver element 230 and decouple thermalexpansion of the sensor housing 202 from the acoustic path. The largersize of the cross-sectional area 209 b is sized to accommodate thepressure-induced forces acting on the buffer rod 250. The transmissionof forces into the sensor housing 202 substantially eliminatespressure-induced forces from acting on the acoustic transceiver element230, substantially eliminating the need for pressure compensation,transducer components that are sized to react pressure-induced forces,and/or wetted transducer design constraints.

By decoupling the acoustic transceiver element 230 from the fluidpressure environment, several advantages are observed. For example,fluid/fuel compatibility of the acoustic transceiver element 230 is notrequired. In another example, the acoustic transceiver element 230frequency is not restricted by thickness requirements driven bypressure-induced forces. In another example in which the acoustictransceiver element 230 is a piezo transducer, the piezo thicknessrequired to support fluid pressure puts the operating frequency of theacoustic transceiver element 230 far below operating requirements oftime of flight measurement. In yet another example, the operationalfrequency of the acoustic transceiver element 230 can be sized toimprove acoustic optimization and/or low flow measurement accuracy.

FIGS. 5A-5C show conceptual examples of incident wave traversal in anultrasonic flow measurement system 500. In some implementations, theUSFM system 500 can be an example of the USFM system 100 of FIG. 1 . TheUSFM system 500 includes two acoustic emitters 510 a and 510 b, twoacoustic receivers 512 a and -512 b, and a fluid control conduit 520. Afluid flows along the fluid control conduit 520 in a directionrepresented by arrow 501.

The derivation that follows assumes that the acoustic receivers 512 aand 512 b are aligned with their respective acoustic emitters 510 a and510 b, perpendicular to the major axis of the fluid control conduit 520.Therefore, the below derivation omits angles of incidence. If theacoustic emitters 510 a, 510 b and acoustic receivers 512 a, 512 b wereplaced off axis, the following derivation could be re-derived using anangle of incidence. However, for simplicity, the trigonometry used tocompensate for such angles is not used here.

Referring to FIG. 5A, first, the speed of sound traveling through anon-moving fluid is considered:Distance=Velocity×time

Or:

Length(L) = Speed  of  sound  in  fluid  (C_(fluid)) × time(t)∴ L₁ = C_(fluid) × t₁$t_{1} = \frac{L_{1}}{C_{fluid}}$

Where C fuel is the speed of sound in fluid, L₁ is the distance betweenthe acoustic transmitter 510 a and the acoustic receiver 512 a, and t₁is the signal transit time between the acoustic transmitter 510 a andthe acoustic receiver 512 a.

Assuming that the direction 501 in which the control volume (fluid) ismoving is the same as a direction of sound travel, represented by line502 a from the acoustic transmitter 510 a to the acoustic receiver 512a, the speed of the sound wave traveling through the fluid will changerelative to the speed of the fluid.

∴ L₂ = V₂ × t₂V₂ = V_(fluid) + C_(fluid)∴ L₂ = (V_(fluid) + C_(fluid))t₂$t_{2} = \frac{L_{2}}{\left( {C_{fluid} + V_{fluid}} \right)}$

Where V_(fluid) is the average velocity of moving fluid, L₂ is thedistance between the acoustic transmitter 510 a and the acousticreceiver 512 a, and t₂ is the signal transit time between the acoustictransmitter 510 a and the acoustic receiver 512 a.

Referring now to FIG. 5B, it is assumed that the control volume (fluid)is opposing the direction of the sound travel from the acoustic emitter510 b to the acoustic receiver 512 b, represented by line 502 b. Thespeed of the sound wave traveling through the fluid will change relativeto the speed of the fluid.

∴ L₃ = V₃ × t₃V₃ = V_(fluid) + C_(fluid)∴ L₃ = (−V_(fluid) + C_(fluid))t₃$t_{3} = \frac{L_{3}}{\left( {C_{fluid} + V_{fluid}} \right)}$

Where L₃ is the distance between the acoustic emitter 510 b and theacoustic receiver 512 b, and t₃ is the signal transit time between theacoustic emitter 510 b and the acoustic receiver 512 b.

Referring for FIG. 5C, for a particular set of ultrasonic sensors, thedevices can both emit and receive signals. This means that for a pair ofsignals, the following characteristics are shared:

L_(up)=L_(down)=L=distance between emitters;

D=diameter ∴ Area of the fluid control conduit 520;

A=cross section area;

C_(fluid)=speed of sound in fluid;

V_(fluid)=velocity of fluid;

ρ_(fluid)=density of fluid;

Z_(fluid)=Acoustic impedance of fluid.

With the above properties shared, the difference in time between theupstream and downstream signal will allow calculation of various fluidcharacteristics.

Upstream and downstream transit times become:

$t_{up} = \frac{L_{up}}{\left( {C_{fluid} - V_{fluid}} \right)}$$t_{down} = \frac{L_{down}}{\left( {C_{fluid} + V_{fluid}} \right)}$

Solving for t_(up), t_(down), and C_(fluid):

$C_{fluid} = \frac{\left( {L_{down} - {t_{down}V_{fluid}}} \right)}{t_{down}}$$C_{fluid} = \frac{\left( {L_{up} + {t_{up}V_{fluid}}} \right)}{t_{up}}$

Since speed of sound is common between the transducers, the speeds ofsound are equal to one another and allows fluid velocity to be found:

C_(fluid) = C_(fluid)$\frac{\left( {L_{down} - {t_{down}V_{fluid}}} \right)}{t_{down}} = \frac{\left( {L_{up} + {t_{up}V_{fluid}}} \right)}{t_{up}}$L_(down)t_(up) − t_(down)t_(up)V_(fluid) = L_(up)t_(down) + t_(up)t_(down)V_(fluid)L_(down)t_(up) − L_(up)t_(down) = t_(up)t_(down)V_(fluid) + t_(down)t_(up)V_(fluid)L_(up) = L_(down) L(t_(up) − t_(dn)) = 2V_(fluid)t_(up)t_(down)$V_{fluid} = \frac{L\left( {t_{up} - t_{down}} \right)}{2t_{up}t_{down}}$

Knowing the velocity of the fluid allows the volume fluid flow(Q_(fluid)) to be determined, where C_(d) is a predetermined dischargecoefficient of the fluid in the fluid control conduit 520:Q _(fluid) =C _(d)×A×V_(fluid)

Fluid sound speed properties can also be determined. Since the fluidvelocity is shared between the pair of transducers the fluid velocitycan be solved. Recalling that:

$t_{up} = \frac{L_{up}}{\left( {C_{fluid} - V_{fluid}} \right)}$

And:

$t_{down} = \frac{L_{down}}{\left( {C_{fluid} + V_{fluid}} \right)}$

Solving t_(up) and t_(down) for V_(fluid):V _(fluid)=(L _(down) −t _(down) C _(fluid))/t _(down)V _(fluid)=(−L _(up) +t _(up) C _(fluid))/t _(up)

Since velocity of the fluid is common between the transducers, theprevious two equations equal one another and allow fluid sound speed tobe solved:

V_(fluid) = V_(fluid)$\frac{\left( {L_{down} - {t_{down}C_{fluid}}} \right)}{t_{down}} = \frac{\left( {{- L_{up}} + {t_{up}C_{fluid}}} \right)}{t_{up}}$L_(down)t_(up) − t_(down)t_(up)C_(fluid) = −L_(up)t_(down) + t_(up)t_(down)C_(fluid)L_(down)t_(up) + L_(up)t_(down) = t_(up)t_(down)C_(fluid) + t_(down)t_(up)C_(fluid)L_(up) = L_(down) L(t_(up) + t_(down)) = −2C_(fluid)t_(up)t_(down)$C_{fluid} = \frac{L\left( {t_{up} + t_{down}} \right)}{2t_{up}t_{down}}$

FIGS. 6A and 6B are graphs that show example incident waves and echoesin the ultrasonic flow measurement system of FIG. 1 . FIG. 6A shows agraph 600 of acoustic amplitude over time, including a sub-duration 601.FIG. 6B shows a graph 602 in which the sub-duration 601 has beenexpanded for visibility.

The graph 600 shows a representation of the emission of an initialincident wave 610 (e.g., when the acoustic transceiver element 230 isactivated to send an acoustic “ping”). An echo 620 is received a fewmilliseconds later. In some implementations, the echo 620 can be theecho 320 of FIG. 3 , which is a reflection of a portion of the incidentwave 310 off the face 262 of the cavity 260.

An echo 630 is received a few milliseconds later. In someimplementations, the echo 630 can be the echo 340, which is a reflectionof a portion of the incident wave 330 off the axial end 254, which isalso an interface to the fluid. Echoes 640, 650, and 660 representreverberations in the buffer rod 250. In operation, the echoes 640-660can be filtered out or otherwise ignored.

An incident wave 670 represents a portion of the incident wave that isreceived by an acoustic sensor (e.g., the acoustic transceiver element230 located downstream or otherwise opposite the acoustic transceiverelement 230 that transmitted the incident wave). The amount of timetaken by the incident wave 670 to arrive is affected by severalvariables, such as the fluid density, flow rate, and flow direction ofthe fluid in the fluid control conduit 130, and the distance 150. Theamount of time taken for the incident wave 670 can be used as t_(up) orf_(down) (e.g., depending on whether the wave travelled upstream ordownstream in the fluid control conduit 130).

As illustrated in FIG. 4 , the buffer rod 250 is designed to transferpressure-induced forces to the face 210 of the sensor housing 202. Thisis achieved through the double diameter construction of the buffer rod250, where the smaller cross-sectional area is sized to accommodate theacoustic transceiver element 230 and decouple thermal expansion of thesensor housing 202 from the acoustic path. The larger cross-sectionalarea of the axial buffer portion 256 b is sized to accommodate thepressure-induced forces acting on the buffer rod 250. The transmissionof forces into the sensor housing 202 substantially eliminatespressure-induced forces from acting on the acoustic transceiver element230 and substantially eliminates the need for (e.g., piezo ceramic)pressure compensation, sizing to react the pressure induced forces, andsubstantially avoids wetted transducer design constraints.

By decoupling the acoustic transceiver element 230 from the fluidpressure environment, several advantages are observed. For example,fluid/fuel compatibility of the acoustic transceiver element 230 is notrequired, the acoustic transceiver element 230 frequency is notrestricted by thickness requirements driven by pressure induced forces,the thickness of the acoustic transceiver element 230 required tosupport fluid pressure puts operating frequency far below operatingrequirements of time of flight measurement, and acoustic transducerfrequency can be sized for acoustic optimization and low flowmeasurement accuracy.

For aircraft turbine fuel systems, mass fuel flow rate can be determinedfor an understanding of combustion energy content. This is solvedthrough the use of the buffer rod 250. The internal design of the bufferrod 250 enables additional acoustic benefits which can be intentionallydesigned into the USFM system 100. For example, the configuration of thebuffer rod 250 enables the controller 190 to determine reflectioncoefficients for fuel acoustic impedance measurement. This is achievedby introducing a transducer transmit amplitude response (e.g., echoes320 or 620), achieved with the cavity 260 which acts as a substantiallyideal reflector, and this amplitude can be compared to the return echoesof the buffer rod fluid interface (e.g., echoes 340 or 630). In someembodiments, the sensitivity of the axial end 254 is further enhanced bythe matching layer 280, however, this will be ignored in order tosimplify the equations below.

Fluid acoustic impedance can be determined by setting echo reflectioneffective areas equal to one another, for example by configuring thecross-sectional areas 209 a and 209 c appropriately. In someimplementations, the areas can be non-equal, and a mathematicalcompensation can be integrated into the process. However, for the sakeof clarity, the areas are assumed to be equal in the equations below.This allows for direct measurement of the reflection coefficient. Thewave propagation within the buffer rod 250 is articulated such that inair, the echo returned from the face 262 is equivalent to the echo fromthe axial end 254.

The reflection coefficient is found through the use of short timeFourier transforms (STFT). The fast Fourier transforms (FFT) of the twoechoes are found to determine the peak of the return echoes:STFT→Amplitude=f(Frequency)

Therefore:|A|=|FFT(Echo₁)|_(f=f) ₀|B|=|FFT(Echo₂)|_(f=f) ₀

Where:

Echo₁ is one of the echoes 320 or 620 of FIGS. 3, 6A, and 6Brespectively, Echo₂ is one of the echoes 340 or 630 of FIGS. 3, 6A, and6B respectively, and f and f₀ are the transducer driving frequency. Thereflection coefficient is then found from:

$R = \frac{A}{B}$

And, assuming the buffer rod 250 is in direct interface with the fluidor fuel (e.g., no matching layer 280 in this case):

$R = \frac{Z_{2} - Z_{1}}{Z_{2} + Z_{1}}$

Where R is the reflection coefficient.

Z₂ = Z_(fluid) Z₁ = Z_(buffer)$Z_{fluid} = \frac{Z_{buffer}\left( {1 - R} \right)}{1 + R}$

The impedance of the buffer rod 250 can be determined throughcharacterization at the sensor level. With the buffer rod impedanceknown and the reflection coefficient being measured, the fluid impedancecan now be solved for:Z _(fluid)=ρ_(fluid) C _(fluid)

From the equations above, a speed of sound in fluid was solved. Sincefluid impedance and fluid sound speed are known, fluid density can nowbe solved.

$\rho_{fluid} = \frac{Z_{fluid}}{C_{fluid}}$

Explicitly:

$\rho_{fluid} = \frac{\left( \frac{\left. {Z_{buffer}\left( {1 - R} \right)} \right)}{1 + R} \right)}{\left( \frac{L\left( {t_{up} + t_{down}} \right)}{2t_{up}t_{down}} \right)}$

With volumetric fluid flow and density now known, the mass fluid flowrate can be found:

${\overset{.}{m}}_{fluid} = {{Q_{fluid}\rho_{fluid}} = {C_{d}{AV}_{fluid}\frac{Z_{fluid}}{C_{fluid}}}}$

FIG. 7 is a flow chart that shows an example of a process 700 fordetermining a fluid reflection coefficient. In some implementations, theprocess 700 can be used with the example ultrasonic sensor module 200 ofFIGS. 1-2B.

At 710, a first emitter is activated to emit at least one incident wave.For example, the example acoustic transceiver element 230 can beactivated to emit an indecent wave.

At 720 the incident wave is transmitted along a buffer rod having afirst axial end abutted to the first emitter and a second axial endopposite the first axial end. For example, the incident wave canpropagate through the buffer rod 250.

At 730 a first echo of the incident wave is reflected by a gap definedalong a portion of the buffer rod. For example, the portion of theincident wave 310 can encounter the face 262 of the cavity 260 and bereflected as the echo 320.

At 740, the first echo is detected. For example, the echo 620 of FIGS.6A and 6B can be detected.

At 750 a first amplitude of the first echo is determined. For example, aFFT can be performed on the echo 620 to determine an amplitude of theecho 620 (e.g., amplitude A as described above).

At 760 a second echo of the incident wave is reflected by the secondaxial end. For example, the portion of the incident wave 330 isreflected off the axial end 254 as the echo 340. In someimplementations, the second echo can be reflected by a ¼ λ matchinglayer affixed to the second axial end, for example, the matching layer280 at the axial end 254.

At 770, the second echo is detected. For example, the echo 630 of FIGS.6A and 6B can be detected.

At 780, a second amplitude of the second echo is determined. Forexample, a FFT can be performed on the echo 640 to determine anamplitude of the echo 640 (e.g., amplitude B as described above).

At 790, a reflection coefficient based on the first amplitude and thesecond amplitude can be determined. For example:

$R = \frac{A}{B}$

FIG. 8 is a flow chart that shows an example of a process 800 fordetermining a mass fluid flow. In some implementations, the process 800can be used with the example USFM system 100 of FIG. 1 .

At 805, a reflection coefficient value is received. For example, Forexample, the reflection coefficient R determined at 790 can be received.

At 810, a fluid acoustic impedance of a fluid at the second axial end isdetermined based on the determined reflection coefficient and apredetermined buffer rod acoustic impedance. For example, the reflectioncoefficient R can be used along with the predetermined buffer rodimpedance Z_(buffer) to determine Z_(fluid), as described above.

At 815, a portion of the incident wave is transmitted at the secondaxial end through the fluid to a sensor arranged a predetermineddistance away from and opposite the first emitter, where the fluid iswithin a tubular fluid conduit having a predetermined cross-sectionalarea. For example, the incident wave 670 of FIG. 6A can travel throughthe fluid from the ultrasonic sensor module 200 that is upstream to theultrasonic sensor module 200 that is downstream.

At 820, the second sensor detects the portion of the incident wave. Forexample, the ultrasonic sensor module 200 that is downstream can detectthe incident wave 670.

At 825, a first time of flight of the portion of the incident wave isdetermined based on the detected portion of the incident wave. Forexample, t_(down) can be determined.

At 830, another incident wave is transmitted, by a second emitter,through the fluid to the first sensor. For example, the ultrasonicsensor module 200 that is downstream can be activated to emit anotherindecent wave upstream.

At 835, the first sensor detects the other incident wave, and at 840 asecond time of flight of the other incident wave is determined based onthe detected other incident wave. For example, t_(up) can be determined.

At 845, a velocity of the fluid within the tubular fluid conduit isdetermined. For example, V_(fluid) can be determined as:

$V_{fluid} = \frac{L\left( {t_{up} - t_{down}} \right)}{2t_{up}t_{down}}$

At 850, a speed of sound within the fluid is determined. For example,C_(fluid) can be determined as:

$C_{fluid} = \frac{L\left( {t_{up} + t_{down}} \right)}{2t_{up}t_{down}}$

At 855, a mass fluid flow rate is determined based on at least thepredetermined cross-sectional area, the determined velocity of thefluid, the determined fluid acoustic impedance, and the determined speedof sound. For example:

${\overset{.}{m}}_{fluid} = {{Q_{fluid}\rho_{fluid}} = {C_{d}{AV}_{fluid}\frac{Z_{fluid}}{C_{fluid}}}}$

In some implementations, one or both of the first emitter and the firstsensor can be piezo elements. In some implementations, the piezo elementcan include the first emitter and the first sensor. For example, theemitter and sensor can be separate components, or the acoustictransceiver element 230 can perform the emitting and detecting functionswithin the ultrasonic sensor module 200.

FIG. 9 is a flow chart that shows an example of a process 900 forresisting effects of fluid exposure on the acoustic transceiver element230 of the example ultrasonic sensor module 200 of FIGS. 1-4 . At 910, asensor is provided. The sensor includes a sensor housing having aninterior surface defining a sensor axis and an axial interior sensorhousing cavity having a first axial sensor housing portion having afirst cross-sectional area perpendicular to the sensor axis, a secondaxial sensor housing portion arranged adjacent to the first axial sensorhousing portion along the sensor axis and having a secondcross-sectional area larger than the first cross-sectional areaperpendicular to the sensor axis, and a face extending from the interiorsurface of the first axial housing portion to the interior surface ofthe second housing portion, a buffer rod having a first axial end and asecond axial end opposite the first axial end and having a first axialbuffer portion arranged within the first housing portion and having thefirst axial end, a second axial buffer portion arranged within thesecond housing portion and abutting the face, and having the secondaxial end, and a third axial buffer portion, extending axially betweenthe first axial buffer portion and the second axial buffer portion, andhaving a third cross-sectional area, smaller than the firstcross-sectional area, perpendicular to the sensor axis, and an acoustictransceiver element acoustically mated to the first end. For example,the ultrasonic sensor module 200 can be provided.

At 920, a fluid is provided at the second axial end. For example, thefluid 301, such as a fuel, can be provided in the fluid cavity 120 a or120 b so as to contact the axial end 254.

At 930, the buffer rod and the sensor housing blocks fluid flow from thesecond end to the acoustic transceiver element. For example, asdiscussed in the description of FIG. 4 , the acoustic transceiverelement 230 is separated from the fluid 301 by the sensor housing 202and the buffer rod 250, and the fluid 301 by the sensor housing 202 andthe buffer rod 250 are configured to prevent the fluid 301 from flowingto the acoustic transceiver element 230.

In some implementations, fluid flow from the second end to the acoustictransceiver element can be blocked by the sensor housing and the secondaxial buffer portion. For example, the fluid 301 is prevented fromflowing to the acoustic transceiver element 230 by interference betweenthe sensor housing 202 and the axial buffer portion 256 b.

At 940, a fluid pressure is applied against the second axial end toproduce an axial force against the buffer rod. For example, the fluidforce 410 can be applied against the axial end 254.

At 950, the buffer rod transmits the axial force to the sensor housing.For example, the buffer rod 250 transmits the force 420 to the sensorhousing 202.

At 960, the sensor housing prevents transmission of the axial force tothe acoustic transceiver element. In some implementations, the process900 can also include transmitting, by the second axial portion, theaxial force to the face, wherein the face interferes with axial movementof the buffer rod toward the acoustic transceiver element. For example,any movement of the buffer rod 250 into the sensor cavity 204 isprevented by the counteractive force 430 created through contact betweenthe axial buffer portion 256 b and the face 210.

FIG. 10 is a schematic diagram of an example of a generic computersystem 1000. The system 1000 can be used for the operations described inassociation with the process 700, 800, and/or 900 according to oneimplementation. For example, the system 1000 may be included in thecontroller 190.

The system 1000 includes a processor 1010, a memory 1020, a storagedevice 1030, and an input/output device 1040. Each of the components1010, 1020, 1030, and 1040 are interconnected using a system bus 1050.The processor 1010 is capable of processing instructions for executionwithin the system 1000. In one implementation, the processor 1010 is asingle-threaded processor. In another implementation, the processor 1010is a multi-threaded processor. The processor 1010 is capable ofprocessing instructions stored in the memory 1020 or on the storagedevice 1030 to display graphical information for a user interface on theinput/output device 1040.

The memory 1020 stores information within the system 1000. In oneimplementation, the memory 1020 is a computer-readable medium. In oneimplementation, the memory 1020 is a volatile memory unit. In anotherimplementation, the memory 1020 is a non-volatile memory unit.

The storage device 1030 is capable of providing mass storage for thesystem 1000. In one implementation, the storage device 1030 is acomputer-readable medium. In various different implementations, thestorage device 1030 may be a floppy disk device, a hard disk device, anoptical disk device, or a tape device.

The input/output device 1040 provides input/output operations for thesystem 1000. In one implementation, the input/output device 1040includes a keyboard and/or pointing device. In another implementation,the input/output device 1040 includes a display unit for displayinggraphical user interfaces. In another implementation, input/outputdevice 1040 includes a serial link, (e.g., Ethernet, CAN, RS232, RS485,optical fiber), for example, to interface to a remote host and/or tosend measurement results, either in a command/response protocol, or atsome periodic update rate after a short initialization period (e.g., <1sec). In another implementation the input/output device 1040 includes adata bus connection to a second computer system or processor.

The features described can be implemented in digital electroniccircuitry, or in computer hardware, firmware, software, or incombinations of them. The apparatus can be implemented in a computerprogram product tangibly embodied in an information carrier, e.g., in amachine-readable storage device for execution by a programmableprocessor; and method steps can be performed by a programmable processorexecuting a program of instructions to perform functions of thedescribed implementations by operating on input data and generatingoutput. The described features can be implemented advantageously in oneor more computer programs that are executable on a programmable systemincluding at least one programmable processor coupled to receive dataand instructions from, and to transmit data and instructions to, a datastorage system, at least one input device, and at least one outputdevice. A computer program is a set of instructions that can be used,directly or indirectly, in a computer to perform a certain activity orbring about a certain result. A computer program can be written in anyform of programming language, including compiled or interpretedlanguages, and it can be deployed in any form, including as astand-alone program or as a module, component, subroutine, or other unitsuitable for use in a computing environment.

Suitable processors for the execution of a program of instructionsinclude, by way of example, both general and special purposemicroprocessors, and the sole processor or one of multiple processors ofany kind of computer. Generally, a processor will receive instructionsand data from a read-only memory or a random access memory or both. Theessential elements of a computer are a processor for executinginstructions and one or more memories for storing instructions and data.Generally, a computer will also include, or be operatively coupled tocommunicate with, one or more mass storage devices for storing datafiles; such devices include magnetic disks, such as internal hard disksand removable disks; magneto-optical disks; and optical disks. Storagedevices suitable for tangibly embodying computer program instructionsand data include all forms of non-volatile memory, including by way ofexample semiconductor memory devices, such as EPROM, EEPROM, and flashmemory devices; magnetic disks such as internal hard disks and removabledisks; magneto-optical disks; and CD-ROM and DVD-ROM disks. Theprocessor and the memory can be supplemented by, or incorporated in,ASICs (application-specific integrated circuits).

To provide for interaction with a user, the features can be implementedon a computer having a display device such as a CRT (cathode ray tube)or LCD (liquid crystal display) monitor for displaying information tothe user and a keyboard and a pointing device such as a mouse or atrackball by which the user can provide input to the computer.

The features can be implemented in a computer system that includes aback-end component, such as a data server, or that includes a middlewarecomponent, such as an application server or an Internet server, or thatincludes a front-end component, such as a client computer having agraphical user interface or an Internet browser, or any combination ofthem. The components of the system can be connected by any form ormedium of digital data communication such as a communication network.Examples of communication networks include, e.g., a LAN, a WAN, and thecomputers and networks forming the Internet.

The computer system can include clients and servers. A client and serverare generally remote from each other and typically interact through anetwork, such as the described one. The relationship of client andserver arises by virtue of computer programs running on the respectivecomputers and having a client-server relationship to each other.

FIG. 11 is a cross-sectional diagram of an example baseline ultrasonicflow measurement (USFM) system 1100. In some embodiments, the system1100 can be a modification of the example ultrasonic flow measurement(USFM) system 100 of FIG. 1 . For the purpose of comparison, generallyspeaking, the system 1100 is presented as a baseline configurationagainst which several examples of USFM systems having additional flowconditioning features can be compared (e.g., the USFM systems discussedin the descriptions of FIGS. 12-19 ).

The USFM system 1100 includes a fluid housing 1110 and two ultrasonicsensor modules 1102. In some embodiments, the sensor modules 1102 can bethe example ultrasonic sensor modules 200 of FIGS. 1 and 2A. The fluidhousing 1110 includes an axial fluid housing cavity 1120 a defined by aninterior surface 1121 a, and an axial fluid housing cavity 1120 bdefined by an interior surface 1121 b. A fluid port 1122 a defines afluid path 1124 a connected to the fluid cavity 1120 a. A fluid port1122 b defines a fluid path 1124 b connected to the fluid cavity 1120 b.The fluid housing 1110 also defines a cavity 1126 that extends betweenthe fluid cavity 1120 a and the 1120 b. The cavity 1126 defines a fluidpath 1132 along a conduit axis 1134. The cavity 1126 fluidicallyconnects the fluid cavity 1120 a and the fluid cavity 1120 b, puttingthe fluid cavity 1120 a in fluidic communication with the fluid cavity1120 b.

Referring briefly to FIG. 17 , a collection of example computationalfluid dynamics (CFD) models of fluid flows through various exampleultrasonic flow measurement systems is shown. Column 1701 shows modelsof fluid flows at minimum flow (e.g., a minimum expected flow for aparticular application, such as minimum fuel flow needed for engineoperation). Column 1702 shows models of fluid flows at mid flow (e.g., amedian expected flow for a particular application). Column 1703 showsmodels of fluid flows at maximum flow (e.g., a maximum expected flow fora particular engine or other application, such as maximum engineapplication fuel flow needs). In some implementations, the minimumflows, mid flows, and maximum flows can be based on a 100:1 turn downratio to cover some applications, and as application flow requirementschange, the definitions of minimum, mid, and maximum flows can change aswell.

Row 1710 shows example models of the minimum, midrange, and maximumflows of the example USFM 1100 or the USFM 1200. As shown in row 1710,the flows exhibit substantial non-linearities (e.g., unconditioned flowbehavior) in their flows. The design of the system 1100 suffers from thefollowing: non-symmetric velocity profiles near the faces of thetransducers, axis asymmetry in the flow body, significant change invelocity profile from min to max flow (e.g., this can drive a largechange in correction factors), and/or flow attachment to the flow body.

Returning to FIG. 11 , the example flow behaviors shown in row 1710 areat least partly attributable to the redirections of flow away from thefluid path 1124 a toward the fluid path 1132, and again as the fluidflow along the fluid path 1132 is redirected toward the fluid path 1124b.

As a general rule of thumb of fluid dynamics, it can take 10 or morelengths-to-diameters (L/D) of straight pipe following a disturbance fora fluid flow to stabilize. In some embodiments, flow conditioning can bebased on Reynold's number (e.g., Re, ratio of dynamic/staticviscosities), roughness of the interior surface of the flow conduit,coefficient of discharge (e.g., Cd, represents the blocking factor of anorifice or other obstruction in the flow path), and other factors thatcan affect fluid flow. In such cases, fully developed flow may onlybegin to occur a substantial distance downstream of the pipe inlet. Insome implementations, such long pipes may promote stable flow whilenegatively impacting other factors. For example, the length of thecavity 1126 needed to achieve stable flow may exceed the designconstraints of a target application (e.g., the size of the housing 1110needed in order to define a sufficiently long cavity 1126 may not fitwithin the available space of a target design). In another example, thecavity 1126 may become long enough to negatively impact the USFMmeasurement process (e.g., the fluid path 132 may become long enough tocause the transmitted signals to become highly attenuated and difficultto process accurately).

Generally speaking, the cavity 1126 is too short to condition fluid flowalong the fluid path 1132. The system 1100 shows an example flow bodydesign that is an open core concept, where the flow body has open flowarea to the inlets and outlets with the transducers located on the axialends of the housing. In this configuration, fuel flow enters and leavesthe flow body through an unobstructed path. While this design is simpleto manufacture, it comes with fluid dynamic downfalls. The design hasbeen evaluated across a 100:1 turn down ratio. Near the low end of theturn down ratio, the Reynolds numbers are near or are within the laminarregion. Conversely, at the high end of the turn down ratio, the Reynoldsnumber is wholly turbulent. As can be observed through evaluation of theCFD images presented in row 1710 of FIG. 17 .

As discussed above, the USFM system 1100 is provided as a baselineexample against which other USFM configurations can be compared.Examples of flow-conditioning USFM configurations having additionalstructures for conditioning fluid flow will be discussed further in thedescriptions of FIGS. 12-19 .

FIG. 12 is a cross-sectional diagram of an example ultrasonic flowmeasurement system 1200 having a fluid control conduit 1230. In someembodiments, the system 1100 can be a modification of the exampleultrasonic flow measurement (USFM) systems 100 or 1100 of FIGS. 1 and 11.

The USFM system 1200 includes a fluid housing 1210 and two ultrasonicsensor modules 1202 (e.g., sensor apparatus). In some embodiments, thesensor modules 1202 can be ultrasonic transducer apparatus, such as theexample ultrasonic sensor modules 200 of FIGS. 1 and 2A. The fluidhousing 1210 includes an axial fluid housing cavity 1220 a defined by aninterior surface 1221 a, and an axial fluid housing cavity 1220 bdefined by an interior surface 1221 b. A fluid port 1222 a (e.g., afluid inlet) defines a fluid path 1224 a (e.g., an inlet fluid flowpath) connected to the fluid cavity 1220 a. A fluid port 1222 b (e.g., afluid outlet) defines a fluid path 1224 b (e.g., an outlet fluid flowpath) connected to the fluid cavity 1220 b. The fluid housing 1210 alsodefines a cavity 1226 that extends between the fluid cavity 1220 a andthe 1220 b.

The fluid housing 1210 also includes the fluid control conduit 1230 thatdefines a fluid path 1232 along a conduit axis 1234 (e.g., the majoraxis of the fluid control conduit 1230). The fluid control conduit 1230has a conduit inlet 1240 and a conduit outlet 1242, and fluidicallyconnects the fluid cavity 1220 a and the fluid cavity 1220 b, puttingthe fluid cavity 1220 a in fluidic communication with the fluid cavity1220 b. The fluid control conduit 1230 is configured with apredetermined flow geometry to define a linear fluid flow path along themajor axis.

In use, fluid flows in through the fluid port 1222 a, where it flowsalong the fluid path 1224 a. The fluid flow is redirected to flow alongthe fluid path 1232, which is non-parallel to the fluid path 1224 a.Fluid flow exiting the fluid control conduit 1230 is re-directeddirected to flow along the fluid path 1224 b, which is also non-parallelto the fluid control conduit 1230.

The fluid control conduit 1230 has a predetermined flowable area 1236and shape (e.g., square, tapered, and/or curved edges, parallel ortapered walls, to affect fluid flow behavior). In some implementations,the fluid housing 1210 can be used across many applications, and thefluid control conduit 1230 can be an interchangeable, specializedsubcomponent (e.g., an adapter) that can adapt the USFM system 1200 forparticular fluid types, applications, and/or operational conditions.

A collection of fluid seals 1238 are arranged in sealing contact betweenthe fluid control conduit 1230 and the fluid housing 1210. The fluidseals 1238 are configured to prevent fluid leakage flow in parallel withthe flowable area 1236. In some embodiments, the fluid seals 1238 candampen the propagation of vibrations between the fluid control conduit1230 and the fluid housing 1210. In some embodiments, the fluid seals1238 can modify an acoustic interface. For example, the fluid seals canbuffer an acoustic impedance mismatch that might otherwise occur if thefluid control conduit 1230 were arranged in direct contact with thefluid housing 1210 (e.g., the fluid control conduit 1230 can floatwithin the fluid housing 1210 upon the fluid seals 1238).

In some embodiments, the internal bore and/or the outer surface of thefluid control conduit 1230 can be formed with geometrical featuresconfigured to reduce measurement errors induced by the propagation ofhigher mode harmonics of the measurement signal frequency. For example,undesired signal energy can be scattered and/or delayed by features suchas knurling, dimples, threads, grooves, bumps, roughness or any otherappropriate formation that can disperse, attenuate, or otherwise reducethe propagation of ultrasonic signals.

In some embodiments, the fluid control conduit 1230 can have apredetermined internal bore diameter-to-length ratio that is selected toreduce measurement errors induced by the propagation of higher modeharmonics of the measurement signal frequency. For example the fluidcontrol conduit 1230 can be configured with predetermined diameter andlength to have a predetermined fundamental frequency, and that placesthe ultrasonic sensor modules 1202 at the pressure nodes of thefundamental frequency so they receive wave energy at the fundamentalfrequency wavelength.

In some implementations, use of the fluid control conduit 1230 as amodular flow body can allow for various manufacturing methods andfeature types to be integrated easily into the design configuration,such as an integral axis symmetric inlet flow conditioner, and/or anintegral axis symmetric outlet flow conditioner. In some embodiments,the fluid control conduit 1230 can be configured as a removable innerhousing having a predefined geometry, to promote modularity and ease ofserviceability and/or replacement.

FIG. 13A is a cross-sectional diagram of an example ultrasonic flowmeasurement system 1300 having a flow conditioner 1350 and a flowconditioner 1352. In some embodiments, the USFM system 1300 can be amodification of the example ultrasonic flow measurement (USFM) systems100, 1100, or 1200 of FIGS. 1, 11, and 12 .

The USFM system 1300 includes a fluid housing 1210 and the twoultrasonic sensor modules 1202. In general, the USFM system 1300 is afluid flow conditioning apparatus that is configured to provide fluidflow conditioning for ultrasonic flow sensing of the conditioned fluidflow. The fluid housing 1210 is a generally tubular outer housing thatincludes the axial fluid housing cavity 1220 a and the axial fluidhousing cavity 1220 b. The fluid port 1222 a defines the fluid path 1224a connected to the fluid cavity 1220 a. The fluid port 1222 b definesthe fluid path 1224 b connected to the fluid cavity 1220 b. The fluidhousing 1210 also defines the cavity 1226 that extends between the fluidcavity 1220 a and the 1220 b.

The fluid housing 1210 also includes a fluid control conduit 1330 (e.g.,a linear fluid conduit) that defines a fluid path 1332 along a conduitaxis 1334 (e.g., the major axis of the fluid control conduit 1330). Thefluid control conduit 1330 has a conduit inlet 1340 and a conduit outlet1342, and fluidically connects the fluid cavity 1220 a and the fluidcavity 1220 b, putting the fluid cavity 1220 a in fluidic communicationwith the fluid cavity 1220 b. The fluid control conduit 1330 isconfigured with a predetermined flow geometry to define a linear fluidflow path along the major axis. In some embodiments, the fluid controlconduit 1330 can be configured as a removable inner housing to promotemodularity, and to promote and ease of serviceability and/orreplacement.

The USFM system 1300 includes a flow conditioner 1350 in fluidiccommunication with the conduit inlet 1340. The USFM system 1300 alsoincludes a flow conditioner 1352 in fluidic communication with theconduit outlet 1342. The flow conditioner 1350 has a body 1370 having anend 1351 that is distal from the conduit inlet 1340, and an end 1353opposite the end 1351 and defines a fluid conditioner outlet.

FIG. 13B is cylindrical projection (e.g., flattened, unwrapped) view ofthe example flow conditioner 1350. The body 1370 (e.g., housing, shell)surrounds a central cavity 1372. The body 1370 includes a collection ofapertures 1374 (e.g., bores, conduits) that fluidically connect thecentral cavity to the radially outer surface of the flow conditioner1350. A projection 1376 represents the radial location of the fluid port1222 a relative to the body 1370.

In the illustrated examples of FIGS. 13A and 13B, the example flowconditioner 1350 is an axis symmetric flow conditioner. For example, theflow conditioner 1350 is generally cylindrical, and the arrangement ofthe apertures 1374 is arranged symmetrically about the axis of thecylinder. In the illustrated examples, the apertures 1374 are uniformlycircular or cylindrical. In some embodiments, the apertures 1374 can beformed in various sizes, and/or with shapes other than circles orcylinders. For example, some of the apertures 1374 can have larger orsmaller diameters than others. In other examples, some or all of theapertures can be formed as tubular conduits having cross-sections thatare circular, ovoid, elliptical, square, triangular, polyhedral,pseudo-random, or any appropriate combination of these and/or othershapes. In some embodiments, the conductive lengths of the apertures1374 can be smooth and uniform, or may be formed with other appropriateshapes and/or roughness (e.g., straight and smooth, helical andpatterned, tapered and rough).

In the illustrated example, the flow conditioner 1352 has a form that issubstantially identical to the example flow conditioner 1350. The flowconditioner 1352 has a body 1370′ having an end 1357 that is distal fromthe conduit outlet 1342, and an end 1355 opposite the end 1357 anddefines a fluid conditioner inlet. In some embodiments, the flowconditioner at the conduit inlet (e.g., the conduit inlet 1340) can beidentical to or a mirror image of the flow conditioner at the conduitoutlet (e.g., the conduit outlet 1342). In some other embodiments, theflow conditioner at the conduit inlet (e.g., the conduit inlet 1340 )can be different from the flow conditioner at the conduit outlet (e.g.,the conduit outlet 1342), as will be discussed in the descriptions ofFIGS. 15A-17 .

Referring briefly to FIG. 17 , row 1720 shows example models of theminimum, midrange, and maximum flows of the example USFM system 1300. Asshown in row 1720, the flows exhibit substantially improved conditioningcompared to row 1710, such as improved axis symmetry, improved plug flowat high Re, and improved symmetry near the transducer faces whencomparing the inlet to the outlet. The example flow behaviors shown inrow 1720 are at least partly attributable to the effects of the flowconditioner 1350 and 1352 upon fluid flow through the USFM system 1300.The flow conditioner 1350 conditions and redirects conditioned fluidflow, while the flow conditioner 1352 redirects fluid flow and alsoconditions fluid flow.

FIG. 14A is a cross-sectional diagram of another example ultrasonic flowmeasurement system 1400 having a flow conditioner 1450 and a flowconditioner 1452. In some embodiments, the USFM system 1400 can be amodification of the example ultrasonic flow measurement (USFM) systems100, 1100, 1200, or 1300 of FIGS. 1, and 11-13B.

The structure of the example USFM 1400 is substantially similar to thestructure of the example USFM system 1300, with the flow conditioners1350 and 1352 replaced by the flow conditioners 1450 and 1452. The flowconditioner 1450 is in fluidic communication with the conduit inlet1340, and the flow conditioner 1452 is in fluidic communication with theconduit outlet 1342. The flow conditioner 1450 has a body 1470 having anend 1451 that is distal from the conduit inlet 1340, and an end 1453opposite the end 1451.

FIG. 14B is cylindrical projection (e.g., flattened, unwrapped) view ofthe example flow conditioner 1450. The body 1470 (e.g., housing, shell)surrounds a central cavity 1472. The body 1470 includes a collection ofapertures 1474 (e.g., bores, conduits) that fluidically connect thecentral cavity to the radially outer surface of the flow conditioner1450. A projection 1476 represents the radial location of the fluid port1222 a relative to the body 1470.

In the illustrated examples of FIGS. 14A and 14B, the example flowconditioner 1450 is an axis symmetric flow conditioner. For example,flow conditioner 1450 is generally cylindrical, and the arrangement ofthe apertures 1474 is arranged symmetrically about the axis of thecylinder.

In the illustrated example the flow conditioner 1452 has a form that issubstantially identical to the example flow conditioner 1450. In someembodiments, the flow conditioner at the conduit inlet (e.g., theconduit inlet 1340) can be identical to or a mirror image of the flowconditioner at the conduit outlet (e.g., the conduit outlet 1342). Insome other embodiments, the flow conditioner at the conduit inlet (e.g.,the conduit inlet 1340) can be different from the flow conditioner atthe conduit outlet (e.g., the conduit outlet 1342), as will be discussedin the descriptions of FIGS. 15A- 17 .

Referring briefly to FIG. 17 , row 1730 shows example models of theminimum, midrange, and maximum flows of the example USFM 1400. As shownin row 1730, the flows exhibit substantially improved conditioningcompared to row 1710. The example flow behaviors shown in row 1730 areat least partly attributable to the effects of the flow conditioner 1450and 1452 upon fluid flow through the USFM system 1400.

FIG. 15A is a cross-sectional diagram of another example ultrasonic flowmeasurement system 1500 having a flow conditioner 1550 and a flowconditioner 1552. In some embodiments, the USFM system 1500 can be amodification of the example ultrasonic flow measurement (USFM) systems100, 1100, 1200, 1300, or 1400 of FIGS. 1, and 11-14B.

The structure of the example USFM system 1500 is substantially similarto the structure of the example USFM system 1300, with the flowconditioners 1350 and 1352 replaced by the flow conditioners 1550 and1552. The flow conditioner 1550 is in fluidic communication with theconduit inlet 1340, and the flow conditioner 1552 is in fluidiccommunication with the conduit inlet 1340. The flow conditioner 1550 hasa body 1570 having an end 1551 that is distal from the conduit inlet1340, and an end 1553 opposite the end 1551. The flow conditioner 1550also includes a contoured profile 1580 that tapers toward the end 1553.

FIG. 15B is cylindrical projection (e.g., flattened, unwrapped) view ofthe example flow conditioner 1550. The body 1570 (e.g., housing, shell)surrounds a central cavity 1572. The body 1570 includes a collection ofapertures 1574 (e.g., bores, conduits) that fluidically connect thecentral cavity to the radially outer surface of the flow conditioner1550. A projection 1576 represents the radial location of the fluid port1222 a relative to the body 1570.

In the illustrated examples of FIGS. 15A and 15B, the example flowconditioner 1550 is an axis symmetric flow conditioner. For example,flow conditioner 1550 is generally cylindrical, and the arrangement ofthe apertures 1574 is arranged symmetrically about the axis of thecylinder.

In the illustrated example the flow conditioner 1552 has a form that isdifferent from the example flow conditioner 1550. The flow conditioner1550 has a body 1570 having an end 1557 that is distal from the conduitoutlet 1342, and an end 1555 opposite the end 1557. The flow conditioner1552 also includes a contoured profile 1581 that tapers toward the end1555. To promote fluid dynamic axis symmetry, the flow conditioner 1552has been configured to resist asymmetry in the inlet/outlet coring topromote symmetric fuel velocity profiles.

In some embodiments, the flow conditioner at the conduit inlet (e.g.,the conduit inlet 1340) can be identical to or a mirror image of theflow conditioner at the conduit outlet (e.g., the conduit outlet 1342),as was previously discussed in the descriptions of FIGS. 13A-14B.

FIG. 15C is cylindrical projection view of the example flow conditioner1552. A body 1570′ surrounds a central cavity 1572′. The body 1570′includes a collection of apertures 1574′ that fluidically connect thecentral cavity to the radially outer surface of the flow conditioner1552. A projection 1576′ represents the radial location of the fluidport 1222 b relative to the body 1570′.

In the illustrated examples of FIGS. 15A and 15C, the example flowconditioner 1552 is an axis asymmetric flow conditioner. For example,flow conditioner 1552 is generally cylindrical, and the arrangement ofthe apertures 1574′ is arranged asymmetrically about the axis of thecylinder. Axis asymmetry can be introduced within the flow body toencourage and promote axis symmetric fluid velocity profiles. Theinteraction of the flow body to the inlet and outlet cores introducesasymmetry in the USFM system 1500. This asymmetry at the inlets andoutlets to the flow body generates asymmetric fluid dynamic behavior,similar to a nozzle flapper at a non-null state.

In the illustrated example, the flow conditioner 1552 has a form that isdifferent from the example flow conditioner 1550. In some embodiments,the flow conditioner at the conduit inlet (e.g., the conduit inlet 1340)can be identical to or a mirror image of the flow conditioner at theconduit outlet (e.g., the conduit outlet 1342), as was discussed in thedescriptions of FIGS. 13A-14B.

Referring briefly to FIG. 17 , row 1740 shows example models of theminimum, midrange, and maximum flows of the example USFM system 1500. Asshown in row 1740, the flows exhibit substantially improved conditioningcompared to row 1710. The example flow behaviors shown in row 1740 areat least partly attributable to the effects of the flow conditioner 1550and 1552 upon fluid flow through the USFM system 1500. As can beobserved in row 1740 of FIG. 17 , where the flow conditioner 1552 isimplemented as an axis asymmetric fluid flow conditioner, the fluidvelocity profile is nearly axis symmetric across the length of the body.To further promote flow velocity symmetry, flow body contouring in theform of the profiles 1580 and 1581 have been incorporated into thegeometry of the flow bodies. A sigmoid and log function flow shapingfeature has been integrated at the inlet and outlet of the flow body. Insome embodiments, the profiles 1580 and 1581 can improve the performanceof the USFM system 1500. For example, flow symmetry can be improved atthe faces of the transducer (e.g., time transit symmetry, integralaverage of velocity can be centered within the flow body, velocitymatching across flow domain), cavitation control can be improved, flowswirl can be reduced, correction factor across the flow range can beimproved, and minimum flow and maximum flow velocity profiles can bemade more consistent (e.g., reducing the derivative of Re dependent Kfactors).

FIG. 16A is a cross-sectional diagram of another example ultrasonic flowmeasurement system 1600 having a flow conditioner 1650 and a flowconditioner 1652. In some embodiments, the USFM system 1600 can be amodification of the example ultrasonic flow measurement (USFM) systems100, 1100, 1200, 1300, 1400, or 1500 of FIGS. 1, and 11-15C.

The structure of the example USFM system 1600 is substantially similarto the structure of the example USFM system 1300, with the flowconditioners 1350 and 1352 replaced by the flow conditioners 1650 and1652. The flow conditioner 1650 is in fluidic communication with theconduit inlet 1340, and the flow conditioner 1652 is in fluidiccommunication with the conduit outlet 1342. The flow conditioner 1650has a body 1670 having an end 1651 that is distal from the conduit inlet1340, and an end 1653 opposite the end 1651. The flow conditioner 1652has a body 1670′ having an end 1657 that is distal from the conduitoutlet 1342, and an end 1655 opposite the end 1657.

FIG. 16B is cylindrical projection (e.g., flattened, unwrapped) view ofthe example flow conditioner 1650. The body 1670 (e.g., housing, shell)surrounds a central cavity 1672. The body 1670 includes a collection ofapertures 1674 (e.g., bores, conduits) that fluidically connect thecentral cavity to the radially outer surface of the flow conditioner1650. A projection 1676 represents the radial location of the fluid port1222 a relative to the body 1670.

In the illustrated examples of FIGS. 16A and 16 B, the example flowconditioner 1650 is an axis symmetric flow conditioner. For example,flow conditioner 1650 is generally cylindrical, and the arrangement ofthe apertures 1674 is arranged symmetrically about the axis of thecylinder.

In the illustrated example the flow conditioner 1652 has a form that isdifferent from the example flow conditioner 1650. In some embodiments,the flow conditioner at the conduit inlet (e.g., the conduit inlet 1340)can be identical to or a mirror image of the flow conditioner at theconduit outlet (e.g., the conduit outlet 1342), as was previouslydiscussed in the descriptions of FIGS. 13A-14B.

FIG. 16C is cylindrical projection view of the example flow conditioner1652. A body 1670′ surrounds a central cavity 1672′. The body 1670′includes a collection of apertures 1674′ that fluidically connect thecentral cavity to the radially outer surface of the flow conditioner1652. A projection 1676′ represents the radial location of the fluidport 1222 b relative to the body 1670′.

In the illustrated examples of FIGS. 16A and 16C, the example flowconditioner 1652 is an axis asymmetric flow conditioner. For example,flow conditioner 1652 is generally cylindrical, and the arrangement ofthe apertures 1674′ is arranged asymmetrically about the axis of thecylinder.

In the illustrated example, the flow conditioner 1652 has a form that isdifferent from the example flow conditioner 1650. In some embodiments,the flow conditioner at the conduit inlet (e.g., the conduit inlet 1340)can be identical to or a mirror image of the flow conditioner at theconduit outlet (e.g., the conduit outlet 1342), as was discussed in thedescriptions of FIGS. 13A-14B.

Referring briefly to FIG. 17 , row 1750 shows example models of theminimum, midrange, and maximum flows of the example USFM system 1600. Asshown in row 1750, the flows exhibit substantially improved conditioningcompared to row 1710. The example flow behaviors shown in row 1750 areat least partly attributable to the effects of the flow conditioner 1650and 1652 upon fluid flow through the USFM system 1600.

FIG. 18 is a collection of cylindrical projection views of additionalexample outlet flow conditioner configurations. A view 1810, a view1820, and a view 1830 are additional examples of symmetric flowconditioner configurations. A view 1840, a view 1850, a view 1860, aview 1870, and a view 1880 are additional examples of asymmetric flowconditioner configurations. Each of the views 1810-1880 includes a body1801, a collection of apertures 1802, and a projection 1803 thatrepresents the location of a conduit inlet or outlet. In someembodiments, the example views 1810-1880 can be projection views ofinlet flow conditioners, outlet flow conditioners, or both. In someembodiments, any appropriate combination of the flow conditionerconfigurations shown in FIGS. 13A-16C and 18 , and any other appropriateflow conditioner configuration, may be used as inlet flow conditionersand/or outlet flow conditioners in a USFM system.

A number of example flow conditioner configurations have beenillustrated by and discussed in the descriptions of FIGS. 13A-18 .However, flow conditioner configurations are not limited to theillustrated examples. Flow conditioners having different diameters,lengths, shapes, central cavity configurations, aperture sizes, apertureshapes, aperture arrangements, materials, layerings, subconfigurations,and combinations of these any other appropriate flow-conditioningconfiguration can be used.

FIG. 19 is a flow chart that shows an example of a process 1900 forconditioning fluid flow in an example ultrasonic flow measurementsystem. In some implementations, the process 1900 can be used with anyof the example USFM systems 1300, 1400, 1500, and 1600 of FIGS. 13A-16C,and any of the example flow conditioner configurations shown in FIGS.13A-16C and 18 .

At 1910, a fluid flow, flowing along a first fluid flow path, isreceived. For example, fluid can flow into the USFM system 1300 throughthe fluid port 1222 a along the fluid path 1224 a.

At 1920, the fluid flow is conditioned by flowing the fluid flow througha first conditioner inlet of a first fluid flow conditioner. Forexample, the fluid flows from the fluid cavity 1220 a, through the flowconditioner 1350, and to the conduit inlet 1340.

In some implementations, the first fluid flow conditioner can be asecond tubular body extending between a first longitudinal end and asecond longitudinal end opposite the first longitudinal end, where thefirst conditioner inlet can be arranged along the second tubular body,and the second longitudinal end can define the first conditioner outlet.For example, the flow conditioner 1350 has a body 1370 having an end1351 that is distal from the conduit inlet 1340, and an end 1353opposite the end 1351 and defines a fluid conditioner outlet.

In some implementations, the first conditioner inlet can include acollection of ports defined radially through the second tubular body,and conditioning fluid flow by flowing through a first conditioner inletof a first fluid flow conditioner can include flowing the fluid flowthrough the collection of ports. For example, fluid can flow into theflow conditioner 1350 through the apertures 1374.

At 1930, the first fluid flow conditioner redirects the fluid flow awayfrom the first fluid flow path and toward a linear fluid flow path. Forexample, the flow conditioner 1350 redirects the fluid flow away fromthe fluid path 1224 a and toward the fluid path 1332. In the illustratedexample, the redirection is approximately a 90-degree redirection, butin other examples the fluid flow conditioner may cause any otherappropriate redirection of flow (e.g., 45 degrees, 60 degrees, 5degrees, 85 degrees, 135 degrees, 150 degrees, 95 degrees, 175 degrees).

At 1940, fluid flow flows along the linear fluid flow path through afirst conditioner outlet. For example, fluid can flow out through theend 1353 that defines the outlet of the flow conditioner 1350.

At 1950, the fluid flow flows along the linear fluid flow path through afluid conduit having a first tubular body extending from a conduit inletto a conduit outlet arranged opposite the conduit inlet, and configuredwith a predetermined flow geometry. For example, fluid can flow alongthe fluid control conduit 1330.

At 1960, the fluid flow flows through a second conditioner inlet of asecond fluid flow conditioner along the linear fluid flow path. Forexample, fluid can flow from the conduit outlet 1342 through the end1355.

At 1970, the fluid flow is redirected, by the second fluid flowconditioner, away from the linear fluid flow path and toward a secondfluid flow path. For example the flow conditioner 1352 can redirect flowaway from the fluid path 1332 and toward the fluid path 1224 b.

At 1980, the fluid flow is conditioned by flowing the fluid flow througha second conditioner outlet of the second fluid flow conditioner. Forexample, fluid can flow through the flow conditioner 1352 toward thefluid port 1222 b.

In some implementations, the second fluid flow conditioner can include asecond tubular body extending between a first longitudinal end and asecond longitudinal end opposite the first longitudinal end, where thesecond conditioner outlet is arranged along the second tubular body, andthe second conditioner inlet is arranged proximal to the conduit outlet.For example, the flow conditioner 1352 has a body 1370 having an end1357 that is distal from the conduit outlet 1342, and an end 1355opposite the end 1357 and defines a fluid conditioner inlet.

In some implementations, the second conditioner outlet can include acollection of ports defined radially through the second tubular body,and conditioning fluid flow by flowing fluid through a secondconditioner outlet of a second fluid flow conditioner can includeflowing the fluid flow through the collection of ports. For example, thebody 1570′ includes a collection of apertures 1574′ that fluidicallyconnect the central cavity to the radially outer surface of the flowconditioner 1552.

In some implementations, the process 1900 can also include transmittingan ultrasonic signal through the first conditioner outlet, the fluidconduit, and the second conditioner inlet along the linear fluid flowpath, receiving the ultrasonic signal through the second conditionerinlet, and determining a mass flow rate and/or a volume flow rate of thefluid flow based on the received ultrasonic signal. For example theultrasonic sensor modules 1202 can transmit and receive ultrasonicsignals directed along the fluid path 1332 and the conduit axis 1234.

In some implementations, the process 1900 can include at least one oftransmitting and receiving, by an ultrasonic transducer, an ultrasonicsignal through the first conditioner outlet and the fluid conduit alongthe linear fluid flow path, where the first fluid flow conditioner alsoincludes the ultrasonic transducer arranged proximal to the firstlongitudinal end. For example, one of the ultrasonic sensor modules 1202is arranged at the end 1351 of the flow conditioner 1350 such thattransmitted signals are directed out the end 1353 and along the conduitaxis 1234 (e.g., the signals are transmitted downstream relative to theflow of fluid).

In some implementations, the process 1900 can include at least one oftransmitting and receiving, by an ultrasonic transducer, an ultrasonicsignal through the second conditioner outlet and the fluid conduit alongthe linear fluid flow path, where the second fluid flow conditionerincludes the ultrasonic transducer arranged proximal to the secondlongitudinal end. For example, one of the ultrasonic sensor modules 1202is arranged at the end 1357 of the flow conditioner 1352 such thattransmitted signals are directed out the end 1355 and along the conduitaxis 1234 (e.g., the signals are transmitted upstream relative to theflow of fluid).

In some embodiments, such as aerospace-focused flow sensors, the flowmeter designs may have to conform to limitations of size, weight, andperformance (e.g., aircraft UFSMs may need to be be compact,lightweight, and robust to challenging L/D configurations surroundingthe primary element). The example USFM systems 1300, 1400, 1500, 1600 ofFIGS. 13A-16C, and the example flow configurations shown in FIG. 18 ,can provide advantages over known art in the field of ultrasonic flowmeters, especially in the axial configuration. For example, the exampleUSFM systems 1300, 1400, 1500, 1600 can be embodied as integral up anddown stream flow conditioners (e.g., compact) that can reduce oreliminate the need for significant uninterrupted lengths of pipe up anddown stream of the flow body, active flow conditioners followed byuninterrupted pipe length, streamline shaping features (e.g., venturi,sigmoid, log), can reduce or eliminate the need for smooth bendedshaping of the flow meter. In some embodiments, other advantages of amodular flow body can be realized for improvements of a flow sensor,such as improved modularity/scalability, the specific flow range targetcan be achieved through adjustment in the flow body definition (e.g., ifan application requires a slightly higher fuel flow range, the flow bodyinternal diameter can be increased to align with the application needswithout redesigning the entire flow sensor and/or without changing thetransducers), Murphy proofing and clocking features, field-replaceableflow body, improved durability over time, an ability to replace the corenot the entire housing, and/or an integral line-replaceable unitapproach.

In some embodiments, the example USFM systems 1300, 1400, 1500, 1600 canprovide improved cavitation control and/or improved acoustic featurecontrol. For example, an integral flow tube having an internal borediameter to length ratio can be specifically chosen to reducemeasurement errors induced by the propagation of higher mode harmonicsof the measurement signal frequency. In another example, an integralflow tube having an internal bore with impressed geometrical features,such as knurling, dimples, threads, grooves, bumps, can be specificallychosen to reduce measurement errors induced by the propagation of highermode harmonics of the measurement signal frequency, by scattering and/ordelaying the undesired signal energy. In another example, an integralflow tube can be configured to have an internal bore with one or morelayers or coatings of a material or materials having a specifiedthickness and acoustic properties of sound speed, density, and/orimpedance relative to the flow tube material and/or other layers, eachselected to reduce measurement errors induced by the propagation ofhigher mode harmonics of the measurement signal frequency, based onabsorption and/or refraction of the undesired signal energy away fromthe acoustic measurement path. For example, the linear fluid conduit canbe configured to dampen ultrasonic acoustic signals.

In some embodiments, the example USFM systems 1300, 1400, 1500, and 1600can enable precision machining. For example, the modular construction ofthe example USFM systems 1300, 1400, 1500, and 1600 can promote improvedhone, surface smoothness control, and/or feature shaping abilities oftheir component parts during manufacture.

Although a few implementations have been described in detail above,other modifications are possible. In addition, the logic flows depictedin the figures do not require the particular order shown, or sequentialorder, to achieve desirable results. In addition, other steps may beprovided, or steps may be eliminated, from the described flows, andother components may be added to, or removed from, the describedsystems. Accordingly, other implementations are within the scope of thefollowing claims.

What is claimed is:
 1. A fluid flow conditioning apparatus, comprising:a linear fluid conduit having a first tubular body defining a major axisand extending from a conduit inlet to a conduit outlet arranged oppositethe conduit inlet, and configured with a predetermined flow geometry todefine a linear fluid flow path along the major axis; a fluid inletdefining an inlet fluid flow path that is non-parallel to the linearfluid flow path; a first fluid flow conditioner comprising a secondtubular body, wherein a first conditioner inlet comprises a plurality ofports defined radially through the second tubular body, and alongitudinal end of the second tubular body defines a first conditioneroutlet, and arranged proximal the conduit inlet and having the firstconditioner inlet in fluidic communication with the fluid inlet, and thefirst conditioner outlet in fluidic communication with the conduitinlet, and configured to: receive fluid flow through the firstconditioner inlet along the inlet fluid flow path; condition, by thefirst conditioner inlet, fluid flow; and redirect conditioned fluid flowaway from the inlet fluid flow path and through the first conditioneroutlet along the linear fluid flow path along the major axis; a secondfluid flow conditioner arranged proximal the conduit outlet and having asecond conditioner inlet in fluidic communication with the conduitoutlet, and a second conditioner outlet, and configured to: receivefluid flow from the linear fluid flow path along the major axis;redirect fluid flow away from the linear fluid flow path and through thesecond conditioner outlet along an outlet fluid flow path that isnon-parallel to the linear fluid flow path; and condition, by the secondconditioner outlet, fluid flow; and a fluid outlet configured to receivefluid flow from the second conditioner outlet.
 2. The fluid flowconditioning apparatus of claim 1, further comprising a sensor apparatusarranged proximal to another longitudinal end of the second tubular bodyopposite said longitudinal end.
 3. The fluid flow conditioning apparatusof claim 2, wherein the sensor apparatus comprises an ultrasonictransducer apparatus configured to emit and receive ultrasonic signalsalong the linear fluid flow path.
 4. The fluid flow conditioningapparatus of claim 2, wherein the sensor apparatus comprises: a sensorhousing having an interior surface defining a sensor axis and an axialinterior sensor housing cavity comprising: a first axial sensor housingportion having a first cross-sectional area perpendicular to the sensoraxis; a second axial sensor housing portion arranged adjacent to thefirst axial sensor housing portion along the sensor axis and having asecond cross-sectional area larger than the first cross-sectional areaperpendicular to the sensor axis; and a face extending from the interiorsurface of the first axial sensor housing portion to the interiorsurface of the second axial sensor housing portion; a buffer rod havinga first axial end and a second axial end opposite the first axial endand comprising: a first axial buffer portion arranged within the firstaxial sensor housing portion and comprising the first axial end; asecond axial buffer portion arranged within the second axial sensorhousing portion and abutting the face, and comprising the second axialend; and a third axial buffer portion, extending axially between thefirst axial buffer portion and the second axial buffer portion, andhaving a third cross-sectional area, smaller than the firstcross-sectional area, perpendicular to the sensor axis; a cavity definedbetween the interior surface and the third axial buffer portion; and anacoustic transceiver element acoustically mated to the first axial end.5. The fluid flow conditioning apparatus of claim 1, wherein the secondfluid flow conditioner comprises a second tubular body extending betweena first longitudinal end of the second tubular body and a secondlongitudinal end of the second tubular body opposite the firstlongitudinal end, wherein the second conditioner outlet is arrangedalong the second tubular body, and the first longitudinal end definesthe second conditioner inlet.
 6. The fluid flow conditioning apparatusof claim 5, wherein the second conditioner outlet comprises a pluralityof ports defined radially through the second tubular body.
 7. The fluidflow conditioning apparatus of claim 5, further comprising a sensorapparatus arranged proximal to the second longitudinal end.
 8. The fluidflow conditioning apparatus of claim 7, wherein the sensor apparatuscomprises an ultrasonic transducer apparatus configured to emit andreceive ultrasonic signals along the linear fluid flow path.
 9. Thefluid flow conditioning apparatus of claim 1, further comprising: anouter housing defining a cavity, wherein the linear fluid conduit isarranged within the cavity; and one more seals arranged in contactbetween the linear fluid conduit and the outer housing and configured todampen propagation of ultrasonic acoustic signals between the linearfluid conduit and the outer housing.
 10. The fluid flow conditioningapparatus of claim 1, wherein the linear fluid conduit comprises anouter housing, different from the first tubular body, having a firstpredefined geometry, and a removable inner housing arrangedconcentrically within the outer housing and defining the predeterminedflow geometry.
 11. A method of fluid flow conditioning, comprising:receiving a fluid flow, flowing along a first fluid flow path;conditioning the fluid flow by flowing the fluid flow through a firstconditioner inlet of a first fluid flow conditioner arranged proximal aconduit inlet, wherein the first fluid flow conditioner comprises asecond tubular body, wherein a first conditioner inlet is arranged alongthe second tubular body and comprises a plurality of ports definedradially through the second tubular body, and the second tubular bodydefines a first conditioner outlet; redirecting, by the first fluid flowconditioner, the fluid flow away from the first fluid flow path andtoward a linear fluid flow path; flowing the fluid flow along the linearfluid flow path through the first conditioner outlet; flowing the fluidflow along the linear fluid flow path through a fluid conduit having afirst tubular body extending from a conduit inlet to a conduit outletarranged opposite the conduit inlet, and configured with a predeterminedflow geometry; flowing the fluid flow through a second conditioner inletof a second fluid flow conditioner arranged proximal the conduit outletalong the linear fluid flow path; redirecting, by the second fluid flowconditioner, the fluid flow away from the linear fluid flow path andtoward a second fluid flow path ; and conditioning the fluid flow byflowing the fluid flow through a second conditioner outlet of the secondfluid flow conditioner.
 12. The method of claim 11, further comprising:transmitting an ultrasonic signal through the first conditioner outlet,the fluid conduit, and the second conditioner inlet along the linearfluid flow path; receiving the ultrasonic signal through the secondconditioner inlet; and determining at least one of a mass flow rate anda volume flow rate of the fluid flow based on the received ultrasonicsignal.
 13. The method of claim 11, wherein the first fluid flowconditioner comprises a second tubular body extending between a firstlongitudinal end of the second tubular body and a second longitudinalend of the second tubular body opposite the first longitudinal end,wherein the first conditioner inlet is arranged along the second tubularbody, and the second longitudinal end defines the first conditioneroutlet.
 14. The method of claim 13, further comprising flowing the fluidflow through the plurality of ports.
 15. The method of claim 13, furthercomprising at least one of transmitting and receiving, by an ultrasonictransducer, an ultrasonic signal through the first conditioner outletand the fluid conduit along the linear fluid flow path, wherein thefirst fluid flow conditioner further comprises the ultrasonic transducerarranged proximal to the first longitudinal end.
 16. The method of claim11, wherein the second fluid flow conditioner comprises a second tubularbody extending between a first longitudinal end of the second tubularbody and a second longitudinal end of the second tubular body oppositethe first longitudinal end, wherein the second conditioner outlet isarranged along the second tubular body, and the second conditioner inletis arranged proximal to the conduit outlet.
 17. The method of claim 16,further comprising flowing the fluid flow through a plurality of portsdefined radially through the second tubular body.
 18. The method ofclaim 16, further comprising at least one of transmitting and receiving,by an ultrasonic transducer, an ultrasonic signal through the secondconditioner outlet and the fluid conduit along the linear fluid flowpath, wherein the second fluid flow conditioner further comprises theultrasonic transducer arranged proximal to the second longitudinal end.